With increasing sophistication, personal computers interact with users through a variety of multi-media apparatus and techniques. In particular, desktop computers have begun to include small, inexpensive microphones. These microphones allow a user to input sound and voice into computer applications. For instance, sampling program applications can capture, store and modify voice and music information. As another example, speech recognition and synthesis programs can parse human speech and perform program commands based upon the recognized human voice. New uses for sound inputs will continue to expand computer performance.
Unfortunately, several factors hamper the use of these microphones for sound input in desktop computers. The desktop computer, designed for digital purposes, presents a rather hostile environment for audio frequency electronic operation. Desktop computers continuously generate digital signals having spurious electromagnetic frequency components in the audio region. This audio-frequency noise can interfere with and degrade voice and sound signals. Exposed to this interference, program applications can exhibit anomalous and often erroneous behavior. Speech recognition applications, in particular, require fairly high signal-to-noise ratios to extract recognizable words from a stream of sound data. Audio frequency noise degradation can hamper and even prevent proper operation of these human voice and sound applications, especially from microphones that produce very low level signals. The most obvious solution to this problem would be to incorporate a very good amplifier within each desktop computer to adequately separate the sound input from any background audio-frequency noise, boosting sound signals to acceptable levels. However, the desktop computer industry is also subject to severe competitive pressures, requiring any solution for inputting sound data to be functional yet inexpensive. Conventional amplifiers that yield adequate signal-to-noise ratios with little added distortion are often complex to manufacture and too expensive to incorporate into desktop computer applications.
Current apparatus and methods for preamplification of microphone signals in computer systems do not provide a simple, inexpensive approach for amplifying sound inputs while minimizing noise degradation. These current approaches do not provide a high performance microphone preamplifier that is easy to manufacture, with high yields and dependable performance. What is needed is an improved method and apparatus for preamplification of microphone signals for computer applications. An improved apparatus and method for microphone preamplification should provide a simple, inexpensive and dependable approach for simple amplification of sound and human voice signals, while rejecting ambient noise from the desktop computer environment. The improved apparatus and method should provide a flexible approach that easily adapts to any particular desktop computer environment, and that can be incorporated in computer circuitry with inexpensive, readily available parts.